N-Acylcarnosine aluminum salts

ABSTRACT

An N-acylcarnosine aluminum salt of the formula, ##STR1## Wherein R represents a lower alkyl group or a phenyl group, and n is an integer of 2 to 3 is effective for use as a digestive ulcer-remedying or anti-ulcer agent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel N-acylcarnosine compounds, more particularly, to N-acylcarnosine aluminum salts having anti-ulcer effects.

2. Description of the Prior Art

In recent years, there has been a trend toward the increase of patients suffering from a digestive or peptic ulcer, and various attempts have been made to develop remedies for the ulcer.

The present inventors have synthesized a number of compounds and have investigated their pharmaceutical effects. As a result of this investigation, it has been found that N-acylcarnosine compounds of a specific type, which will appear hereinafter, exhibit a significantly excellent digestive ulcerremedying or anti-ulcer effect and are low in toxicity and hence are satisfactory for actual use. Based upon this finding, the present invention has been accomplished.

SUMMARY OF THE INVENTION

Therefore, one object of the present invention is to provide novel N-acylcarnosine aluminum salts.

Briefly, these objects and other objects and advantages of this invention can be attained by an N-acylcarnosine aluminum salt of the formula (I), ##STR2## wherein R represents a lower alkyl group or a phenyl group, and n is an integer of 2 to 3.

DETAILED DESCRIPTION OF THE INVENTION

The N-acylcarnosine aluminum salt of the formula (I) according to the present invention can be prepared, for example, by interacting an N-acylcarnosine of the formula (II), ##STR3## wherein R has the same meaning as defined above, with an aluminum alkoxide or an inorganic aluminum salt by any of the methods described below.

Method 1

An N-acylcarnosine is reacted with an aluminum alkoxide to obtain an N-acylcarnosine aluminum salt of the formula (I).

The N-acylcarnosine useful as one of the starting materials is prepared, for example, by converting the corresponding carboxylic acid to an acid halogenide in any usual manner and then reacting the halogenide with carnosine.

Typical examples of the aluminum alkoxide include aluminum methoxide, aluminum ethoxide, aluminum isopropoxide, aluminum t-butoxide, aluminum cyclohexyloxide and the like. When the aluminum alkoxide contains any impurity such as aluminum hydroxide or a polymer thereof, it is preferable to remove the impurity by distillation, solvent extraction or the like. The reaction is favorably conducted in a suitable solvent at a temperature ranging from room temperature to 80° C. Suitable solvents include water, an organic solvent such as methanol, ethanol, isopropanol or butanol, and a mixture thereof. After completion of the reaction, the solvent and secondarily produced alcohols are removed from the reaction solution to obtain the desired N-acylcarnosine aluminum salt of the formula (I).

Method 2

An N-acylcarnosine is reacted with an inorganic aluminum salt, and the resulting aqueous reaction solution is passed through a column packed with an anion exchange resin to obtain the desired N-acylcarnosine aluminum salt of the formula (I).

Typical examples of the inorganic aluminum salt useful in method 2 include mineral acid salts of aluminum such as aluminum sulfate, aluminum nitrate and aluminum chloride.

The anion exchange resin useful in method 2 may be either a weakly basic resin or a strongly basic resin, and preferably, a weakly basic anion exchange resin such as Amberlite IR-45 is used.

The amount of the anion exchange resin depends on the amount of the ions of a mineral acid and on the type of the ions in an aqueous solution of the N-acylcarnosine and the mineral acid. Too small amounts of such resin adversely cause the mineral acid ions to introduce into an effluent, while excessive amounts induce the adsorption of the N-acylcarnosine to an objectionable degree. Accordingly, it is desirable that the anion exchange resin be used twice or three times equivalent of the N-acylcarnosine.

The concentration of the aqueous solution which is passed through the column is not critical but is preferably held at such a level that the concentration of the mineral acid ions is in the range of about 0.5 to 1 equivalent per liter of the solution. The space velocity is suitably in the range of about 0.5 to 2.

The aqueous solution which has come out of the column is concentrated under reduced pressure and evaporated to dryness to obtain the desired compound of the formula (I).

In either method 1 or method 2 above, when the molar ratio of an N-acylcarnosine to an aluminum alkoxide or an inorganic aluminum salt is varied, an N-acylcarnosine aluminum salt can be prepared which corresponds to such molar ratio.

The N-acylcarnosine aluminum salts typical of and practical for the present invention which were listed as samples A to C were tested to determine their digestive ulcer-curing effects and degrees of toxicity with the results tabulated in the following experimental examples.

Samples: ##STR4##

It will be noted that as control compounds, use was made of L-carnosine, L-glutamine, N-acetyl-L-glutamine aluminum and aluminum sucrose sulfate which are known to have an anti-ulcer effect for purposes of comparison. The anti-ulcer effects and degrees of toxicity of the N-acylcarnosine aluminum salts according to the invention were determined using rats in which instances various gastric ulcer models of rats were utilized to estimate the anti-ulcer effects.

The experimental methods of ulcers and toxicity will be apparent from the following description.

Experiment 1

Shay's ulcer: Groups of ten male Donryu strain rats each weighing 210 to 230 g were deprived of food for 48 hours. The pylorus of each rat was ligated according to the method of Shay et al [Gastroenterology, 5, 43-61 (1945)]. Each of the animals was allowed to stand abstained from food and water for further 14 hours and then sacrificed to remove its stomach. After collection of the gastric juice, the ulcerated area (mm²) in the forestomach of each rat was measured under a dissecting microscope (10×). The total area (mm²) of all the lesions of each rat was indicated as an ulcer index. Test medicine samples were given orally immediately after the pylorus ligation.

The experimental results are shown in Table 1.

                  TABLE 1                                                          ______________________________________                                         Inhibition Effects on Shay's Ulcer in Rats                                                 Dose                                                               Samples     (mg/kg, P.O.)                                                                              Ulcer index                                                                              % Inhibition                                 ______________________________________                                         Control     --          2.4 ± 0.7                                                                             --                                           A           1,000       0.47 ± 0.4                                                                            80.4                                         L-Carnosine 1,000       2.1 ± 0.7                                                                             12.5                                         L-Glutamine 1,000       2.2 ± 0.8                                                                              8.3                                         Aluminum sucrose                                                               sulfate     1,000       0.7 ± 0.8                                                                             71.0                                         Control     --          2.9 ± 0.4                                                                             --                                           B           1,000       0.6 ± 0.8                                                                             79.3                                         N-Acetyl-L-                                                                    glutamine aluminum                                                                         2,000       0.9 ± 0.7                                                                             69.0                                         Aluminum sucrose                                                               sulfate     1,000       0.8 ± 0.6                                                                             72.4                                         ______________________________________                                          A and B have the same meaning as defined above.                          

Experiment 2

Stress ulcer: Groups of ten male Donryu strain rats each weighing 240 to 260 g were placed in a stress cage which served to immobilize the animals therein and then immersed in a water bath of 23° C. on a level with the xiphoid process according to the method of K. Takagi et al [Jap. J. Pharmac., 18 (9), 9-19 (1968)], thereby imposing stress on each rat. Seven hours after the immersion, each of the animals was withdrawn from the water bath and immediately sacrificed by a blow on the head, followed by removal of the stomach of each rat. The stomach was slightly inflated by injecting a 1% formalin solution and then immediately immersed in a 1% formalin solution, followed by incising the stomach along its greater curvature to measure the length (mm) of each lesion in the glandular portion under a dissecting microscope (10×). The total length (mm) of all the lesions of each rat was indicated as an ulcer index. Test medicine samples were given orally ten minutes before the immersion in water.

The results are shown in Table 2.

                  TABLE 2                                                          ______________________________________                                         Inhibitory Effects on Stress Ulcer in Rats                                                 Dose                                                               Samples     (mg/kg, P.O.)                                                                              Ulcer index                                                                              % Inhibition                                 ______________________________________                                         Control     --          15.2 ± 3.2                                                                            --                                           A             300        8.1 ± 2.9                                                                            46.7                                                     1,000        4.5 ± 2.4                                                                            70.4                                         L-Carnosine   300       14.2 ± 3.7                                                                             6.6                                                     1,000       10.7 ± 2.2                                                                            29.6                                         Aluminum sucrose                                                               sulfate     1,000        6.5 ± 6.0                                                                            56.7                                         ______________________________________                                          A has the same meaning as defined above.                                 

Experiment 3

Aspirin-induced ulcer: Groups of ten male Donryu strain rats each weighing 220 to 230 g were deprived of food for 24 hours. The pylorus of each rat was ligated under ether anethesia according to the method of S. Okabe et al [Jap. J. Pharmac. 24, 357-361 (1974)]. After the pylorus ligation, aspirin (100 mg/kg) was administered orally to each rat. Seven hours after the administration, each of the animals was sacrificed under ether anesthesia to remove its stomach. After collection of the gastric juice and treatment with a 1% formalin solution, the length (mm) of each lesion formed in the glandular portion was measured. The total length (mm) of all the lesions of each rat was indicated as an ulcer index. Test medicine samples were given orally immediately after the pylorus ligation.

The results are shown in Table 3.

                  TABLE 3                                                          ______________________________________                                         Inhibitory Effects on Aspirin-induced Ulcer in Rats                                        Dose                                                               Samples     (mg/kg, P.O.)                                                                              Ulcer index                                                                              % Inhibition                                 ______________________________________                                         Control     --          17.7 ± 2.3                                                                            --                                           A           1,000       0.7 ± 0.6                                                                             96.0                                         L-Glutamine 1,000       6.0 ± 2.2                                                                             66.1                                         Aluminum sucrose                                                               sulfate     1,000       3.7 ± 2.1                                                                             79.1                                         ______________________________________                                          A has the same meaning as defined above.                                 

Experiment 4

Indomethacin-induced ulcer: Groups of ten male Donryu strain rats each weighing 200 to 215 g were deprived of food for 24 hours. Then, the pylorus was ligated under ether anethesia, after which indomethacin was administered subcutaneously in an amount of 25 mg/kg to each rat. Seven hours after the administration, each of the animals was sacrificed under ether anethesia to remove its stomach, followed by immersion in a 1% formalin solution for ten minutes. The stomach which had been semi-fixed was incised along its greater curvature, and the length (mm) of each lesion formed in the mucous membrane was measured under a dissecting microscope (10×). The total length (mm) of all the lesions of each rat was indicated as an ulcer index. Test medicine samples were given orally ten minutes before the pylorus logation.

The results are shown in Table 4.

                  TABLE 4                                                          ______________________________________                                         Inhibitory Effects on Indomethacin-induced Ulcer in Rats                                   Dose                                                               Samples     (mg/kg, P.O.)                                                                              Ulcer index                                                                              % Inhibition                                 ______________________________________                                         Control     --          16.3 ± 2.4                                                                            --                                           A           300         6.0 ± 2.4                                                                             63.2                                         L-Carnosine 300         17.3 ± 3.0                                                                            ˜0                                     L-Glutamine 300         9.5 ± 4.1                                                                             41.8                                         Aluminum sucrose                                                               sulfate     300         7.8 ± 3.0                                                                             52.1                                         ______________________________________                                          A has the same meaning as defined above.                                 

Experiment 5

Histamine-induced ulcer: Groups of ten male Donryu strain rats each weighing 210 to 230 g were deprived of food for 48 hours and then administered intraperitoneally with histamine phosphate (300 mg/kg). Four hours after the administration, each of the animals was sacrificed under ether anesthesia, followed by removal of its stomach and immersion in a 1% formalin solution for ten minutes. The stomach which had been semi-fixed was incised along the greater curvature, and the length (mm) of each lesion was measured under a dissecting microscope (10×). The total length (mm) of all the lesions of each rat was indicated as an ulcer index. Test medicine samples were given orally before the histamine administration.

                  TABLE 5                                                          ______________________________________                                         Inhibitory Effects on Histamine-induced Ulcer in Rats                                      Dose                                                               Samples     (mg/kg, P.O.)                                                                              Ulcer index                                                                              % Inhibition                                 ______________________________________                                         Control     --          24.1 ± 4.7                                                                            --                                           A           300          9.4 ± 2.0                                                                            61.0                                         L-Carnosine 300         17.3 ± 3.2                                                                            28.2                                         Aluminum sucrose                                                               sulfate     300         14.4 ± 1.5                                                                            40.2                                         ______________________________________                                          A has the same meaning as defined above.                                 

Experiment 6

Acute toxicity: Male and female Wister strain rats each weighing 150 to 200 g were divided into two groups, respectively, each group consisting of ten rats, and were administered orally with one of the N-acylcarnosine aluminum salts according to the invention. The thus treated rats were visually observed for seven days after the administration.

The results are shown in Table 6.

                  TABLE 6                                                          ______________________________________                                         Values of LD50 in Rats                                                                      LD50 (mg/kg, P.O.)                                                Samples        Male     Female                                                 ______________________________________                                         A              >10,000  >10,000                                                ______________________________________                                          A has the same meaning as defined above.                                 

As is apparent from the experimental results shown in Tables 1 to 6, the N-acylcarnosine aluminum salts according to the invention exhibit an excellent inhibiting effect on various ulcer models. That is, the N-acylcarnosine aluminum salts, when administered orally in an amount of 300 or 1,000 mg/kg to rats in the tests of Shay's ulcer, stress ulcer, aspirin-induced ulcer, indomethanocin-induced ulcer and histamine-induced ulcer, are significantly effective for inhibiting any of the ulcers and hence are more excellent than any existing anti-ulcer agents.

In the acute toxicity test, even when the N-acylcarnosine aluminum salts were administered orally in an amount as large as 10 g/kg, no death of rats was recognized, and no or little change in general symptoms was observed.

Accordingly, the N-acylcarnosine aluminum salts of the present invention can be used as a digestive ulcer remedy which is higher in safety and more excellent in effectiveness than L-glutamine, N-acetyl-L-glutamine aluminum and aluminum sucrose sulfate which have now been widely used as anti-ulcer agents. The N-acylcarnosine aluminum salts may be administered either orally or parenterally and may be used in the form of, for example, tablets, capsules, powders, granules and syrups for oral administration and also in the form of injection for parenteral administration.

The amount of administration is generally in the range of 500 to 5,000 mg/day for adults, which may be varied depending both on the age and on the symptom.

This invention will now be described in more detail with reference to certain specific Examples which are provided for purposes of illustration only and are not intended to be considered as limiting.

EXAMPLE 1

0.816 g of aluminum isopropoxide in 6.6 ml of isopropanol was heated and then stirred at about 60° C. for 30 minutes to which was added 0.536 g of N-acetyl-DL-carnosine. The resulting mixture was stirred at 60° C. for three hours, and then isopropyl alcohol was removed from the reaction mixture under reduced pressure. To the residue was added 10 ml of water, and the mixture was stirred at 60° C. for one hour. Any insoluble materials were removed by filtration, and the filtrate was condensed. To the residue was added isopropyl alcohol for solidification. The resulting solidified aluminum salt was collected by filtration. After sufficient washing with isopropyl alcohol, 0.81 g (quantitative yield) of an N-acetylcarnosine aluminum salt was obtained as colorless powder.

mp: 280° C.<(decomp.)

IRν_(max) ^(KBr) cm⁻¹ : 3500˜3200 (OH), 1660˜1610 (C═O), 1590˜1540 (COO)

NMR (D₂ O)δ: 2.00 (3H, s, --COCH₃), 2.54 (2H, m, --CH₂ CH₂ NH--), 3.44 (4H, m, --COCH₂ CH₂ N<, --CH₂ CH<), 4.68 (1H, m, ##STR5## 7.36, 8.66 (1Hx2, sx2, imidazole ring protons).

Elemental analysis as (C₁₁ H₂₀ N₄ O₉)Al₂ (OH)₅ : Calculated (%): C 32.52, H 4.96, N 13.79, Al 13.28: Found (%): C 32.63, H 5.27, N 13.89, Al 13.31. These analytical data confirm the following structure (A). ##STR6##

EXAMPLE 2

To a solution of 3.13 g of aluminum isopropoxide dissolved in 35 ml of isopropyl alcohol was added 1.37 g of N-acetyl-L-carnosine at 60° C., and the mixture was stirred for one hour until it became homogeneous. 25 ml of water was added to the reaction mixture which was stirred for 30 minutes. Isopropyl alcohol of the mixture was evaporated under reduced pressure, and water was added to the residual solution. The clear solution was freeze dried to obtain 2.5 g (quantitative yield) of an N-acetyl-L-carnosine aluminum salt as colorless powder.

mp: 280° C.<(decomp.)

[α]_(D) ²⁵ : +8.5° C. (C=1% in H₂ O)

IRν_(max) ^(KBr) cm⁻¹ : 3400 (OH), 1640 (CO), 1400

NMR (D₂ O)δ: 1.79 (3H, s, --COCH₃), 2.32 (2H, t, --COCH₂ CH₂ NH--), 3.21 (2H, m, ##STR7## , 3.69 (2H, t, --COCH₂ CH₂ NH--), 4.44 (1H, m, ##STR8## 7.04, 8.17 (1Hx2, sx2, immidazole ring protons)

Elemental analysis as (C₁₁ H₁₅ N₄ O₄)Al₃ (OH)₈ : Calculated (%): C 27.28, H 4.80, N 11.57: Found (%): C 27.34, H 4.62, N 11.65. These analytical data confirm the following structure (B). ##STR9##

EXAMPLE 3

(a) N-Benzoyl-L-carnosine: To a solution of 2.42 g of L-carnosine dissolved in 13 ml of water was added 6.5 ml of acetone. Thereafter, 6.32 g of benzoyl chloride was added dropwise to the solution at such a rate that the reaction mixture did not exceed 20° C. in temperature and was maintained at a pH of 7.0 to 7.5. The dropwise addition took about one hour. After the addition, acetone was evaporated under reduced pressure, and the residue was adsorbed on a strong anion exchange resin (SA-10A) in an amount of 130 ml. The anion resin was washed with water and eluted with 1 N acetic acid, and the eluant was further adsorbed on a strong cation exchange resin (SK-1B) in an amount of 10 ml. After the cation resin was washed with water and eluted with 2% aqueous ammonia, the eluant was evaporated under reduced pressure to remove the greater part of ammonia. The residue was passed through 30 ml of a weak cation exchange resin (IRC-50), and the portion of the residue which had not been adsorbed was distilled to dryness under reduced pressure to obtain a crude product. Recrystallization of the crude product from methanol-acetone gave 1.69 g of N-benzoyl-L-carnosine as colorless crystal (yield: 48%).

mp: 217°˜219° C. (decomp.)

[α]_(D) ²⁵ : +10.3° C. (C=1% in H₂ O)

IRν_(max) ^(KBr) cm⁻¹ : 3280, 1640, 1520, 1385

NMR(D₂ O)δ: 2.48 (2H, t, J=7 Hz, --COCH₂ CH₂ NH--), 3.02 (2H, m, ##STR10## 3.46 (2H, t, J=7 Hz, --COCH₂ CH₂ NH--), 4.37 (1H, m, ##STR11## 6.99 [1H, s, imidazole ring proton (5-position)], 7.1˜7.6 (5H, m, benzene ring protons), 8.14 [1H, s, imidazole ring proton (2-position)].

Elemental analysis as C₁₆ H₁₈ N₄ O₃ : Calculated (%): C 58.16, H 5.50, N 16.96: Found (%): C 58.21, H 5.65, N 16.93.

(b) To a solution of 0.80 g of aluminum isopropoxide dissolved in 15 ml of isopropyl alcohol was added 0.64 g of N-benzoyl-L-carnosine at 60° C. 0.9 g (quantitative yield) of an N-benzoyl-L-carnosine aluminum salt was obtained as colorless powder in the same way as in Example 2.

mp: 235° C. (decomp.)

[α]_(D) ²⁵ : +4.1° C. (C═1% in H₂ O)

IRν_(max) ^(KBr) cm⁻¹ : 3400 (OH), 1630 (CO), 1540

NMR(D₂ O)δ: 2.55 (2H, t, --COCH₂ CH₂ NH--), 3.10 (2H, m, ##STR12## 3.56 (2H, t, --COCH₂ CH₂ NH--), 4.44 (1H, m, ##STR13## 6.99 [1H, s, imidazole ring proton (5-position)], 7.45 (5H, m, benzene ring proton), 8.08 [1H, s, imidazole ring proton (2-position)].

Elemental analysis as (C₁₆ H₁₇ N₄ O₄)Al₂ (OH)₅ : Calculated (%): C 41.03, H 4.74, N 11.96: Found (%): C 40.88, H 4.67, N 11.89. These analytical data confirm the following structure (C). ##STR14## 

What is claimed as new and is intended to be secured by Letters Patent is:
 1. An N-acylcarnosine aluminum salt of the formula (I),
 2. The N-acylcarnosine aluminum salt according to claim 1, wherein n is
 3. The N-acylcarnosine aluminum salt according to claim 1, wherein n is
 4. The N-acylcarnosine aluminum salt according to claim 1, wherein R is a
 5. The N-acylcarnosine aluminum salt according to claim 1, wherein R is a phenyl group. 